Secondary Metabolites Of Two Marine Algous Endophytic Fungi And Their Bioactivities

Marine microorganisms possess highly diverse metabolism pathways. Among them, the research on the secondary metabolites of marine endophytic fungi have drawn the interest of more and more natural product chemists. In this dissertation, on the basis of mycelia'biomass, weight of fermentation extracts, antimicrobial and cytotoxic activities, the results of TLC and HPLC analysis, the static fermentation extracts of 13 endophytic fungal strains (isolated from seaweeds collected along Qingdao coastline) on 4 kinds of liquid cultural mediums, were comprehensively evaluated. And two strains Aspergillus niger EN-1 (isolated from the brown algae Colpomenia sinuosa) and A. versicolor EN-7 (isolated from the brown algae Sargassum thunbergii) were selected as aimed strains to be fermented on 30 liters of GPYM and PDB cultural medium respectively for further investigation of chemical constituents. Most of the isolated compounds were preliminary screened on their bioactivities.The compounds were isolated from the fermentation extracts by repeated column chromatography (CC) on silica gel, RP-18, and Sephadex LH-20, as well as by preparative thin layer chromatography (PTLC), semi-preparative HPLC and recrystallization. The structures of these compounds were elucidated by means of spectroscopic methods including IR, UV, EI-MS, FAB-MS, HR-ESI-MS, 1D-NMR (1H-NMR, 13C-NMR, DEPT) and 2D-NMR (1H-1H COSY, HSQC, HMBC) as well as chemical method. Totally, 55 compounds were structurally elucidated. From the extracts of A. niger EN-13, 31 compounds were isolated and structurally elucidated. Among them, Nine were found to be new compounds, including two new sphingolipids (AN-1~2), three new naphtho-γ-pyrones (AN-3~5), three new phenethyl-α-pyrone derivatives (AN-17, AN-19~20), and a new steroidal Diels-Alder adduct (AN-21). Additionally, a new naturally reported cyclodipeptide (AN-27) were also elucidated. From the extracts of fungus A. versicolor EN-7, 24 compounds were isolated and structurally elucidated. Among them, two were found to be new compounds as new anthraquinones (AV-12, AV-17). In addition, the two new sphingolipids (AN-1~2) from fungus A. niger EN-13 were reisolated from fungus A. versicolor EN-7.Most of the pure compounds were screened for their antimicrobial, DPPH scavenging and cytotoxic activities. It was revealed that the new compounds AN-1, AN-5 and AN-20 exhibited moderate or weak inhibitory activity against Candida albicans, compound AN-4, AN-5 and AN-21 exhibited moderate or weak inhibitory activity against Aspergillus niger, compound AV-12 and AV-17 showed weak inhibitory activity against Escherichia coli. In the DPPH scavenging assay, compound AN-5 showed moderate free radical scavenging activities with an EC50 of 109.3μM, compared with the 81.8μM for positive control BHT. Part of the isolated known compounds also exhibited moderate or weak activity in the antimicrobial and DPPH scavenging assay. None of the tested compounds showed remarkable activity in the in vitro cytotoxic assay against tumor cell lines SMMC-7721 and A-549.